Hydrogen peroxide is a powerful oxidizing agent. It is widely used in bleaching, preparation of chemicals, pollution control, mining and power generation. It is particularly ecologically desirable as a pollution control agent, since it yields only water and/or oxygen upon decomposition.
Most commercial production of hydrogen peroxide is by processes based on the electrolysis of sulphuric acid solution, or the autoxidation of isopropyl alcohol and anthraquinones. It is known to conduct direct oxidation of hydrogen and oxygen in an acidic aqueous solution, using a group VIII noble metal catalyst. Examples of such process are shown in U.S. Pat. Nos. 4,462,978 and 4,661,337 of Brill and U.S. Pat. No. 4,681,751 of Gosser. However, yields in such a process are very low, unless high pressures are used to increase hydrogen and oxygen solubilities and to reduce transfer limitations. High pressures complicate the process by requiring pressure vessels. Further, the carrying out of the process at high pressures increases the risk of explosion.
It is therefore important to develop a process which manufactures hydrogen peroxide at ambient or near ambient temperatures, and at ambient or near ambient pressures.
The present invention accomplishes this by making use of group VIII metal catalysts on a hydrophobic support.
Hydrophobic catalyst supports are already known for other purposes. For example, U.S. Pat. No. 4,025,560 of Rolston et al. shows a catalyst for the exchange of hydrogen isotopes between a gas stream and a water stream where the catalyst is an inherently hydrophobic material such as cubes of polytetrafluorethylene (PTFE), polyethylene or the like. European Patent application 0015585 of Hitachi Inc. shows catalysts similar to those of Rolston for other types of gas-liquid reactions. An activated carbon catalyst which has been reacted with a monomer which forms hydrophobic polymers, is disclosed for carbon monoxide oxidation in U.S. Pat. No. 4,652,537 of Tamura.
Hydrophobic catalysts of this sort have not previously been proposed for the production of hydrogen peroxide. They provide the advantage of much higher yields at ambient pressures and temperatures than previous catalysts used for reaction in an acidic solution. While it is not desired to limit the application by reliance on a particular mechanism of the reaction, ti is believed that the hydrophobic material allows the hydrogen and oxygen to reach the metal sites directly by gas phase diffusion, thus eliminating mass transfer limitations.